Valve gear



Oct. 13, 1959 .1.J. VAN DEUN VALVE GEAR Filed Aug. 4, 1958 muy uu H r ATTORNEYS United States Patent() VALVE GEAR Jules I. Van Deun, Livonia, Mich., assignor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware l Applcanun August 4, 19ss,seria1No. 752,916 3 Claims. (Cl. 123-90) This invention relates to an internal combustion engine valve gear and more particularly to a novel means by which inherent lash problems of a mechanical valve gear train are minimized.

These lash problems can be classilied generally as noise, loss of contact or separation between the cam lobe and the valve tappet and/ or other valve gear parts, and excessive oil leakage resulting from the loss of contact between the lower portion of the rocker arm shaft and the rocker arm. Noise is most prevalent in the gear train prior to the growth of the parts as -a result of thermal expansion. Unless periodically adjusted, the normal engine wear between the parts increases the lash clearance resulting in more and more noise as the valve gear parts separate during the operation of the engine.

These lash problems as well as others are reduced to a commercially acceptable minimum of the applicants device. In his structure, the valve lash is represented by a coil spring between the end of the push rod and the valve tappet. Because the lash is represented by the spring which is located within the connes of the valve tappet, the separation of parts is confined between the push rod end and the inner seat of the valve tappet. Any noise resulting from the push rod end contacting the valve tappet is confined within the valve tappet and, of course, in the cylinder block where it is substantially muffled.

Valve tappet rotation is normally engineered in the valve gear train by making the contact between the cam base circle and the valve tappet one in which the valve tappet contacts the base circle cam centerline at a point offset from the tappet centerline. The applicants spring biased tappet is continuously urged to ride the cam thus decreasing the instances when the tappet leaves the cam resulting in greater valve rotation and increased base circle cam and valve tappet life.

In the normal rocker arm and shaft arrangement, there is a .003 in. to .005 in. clearance between the parts. Normally, the rocker arm is urged in an upward direction so that the bottom of the rocker arm hole bears against the lower part of the rocker shaft separated by a thin layer of oil. If this relationship is disturbed and a greater clearance exists between the bottom of the shaft and the bottom of the rocker arm hole, the predetermined oil leakage between the parts is substantially increased resulting in an excessive amount of oil in the valve chamber cover area. Applicants construction at all times maintains the predetermined relationship between the bottom of the rocker arm hole and the bottom of the rocker shaft.

Other objects and advantages of this invention will be made more apparent as this `description proceeds, particularly when considered in connection with the accompanying drawings, wherein:

Figure 1 is a front elevational view in vertical section and showing a mechanical valve gear train embodying the applicants invention; and,

Figure 2 is an enlarged fragmentary view of the push 4rod and valve tappet portion of the gear train embodyin the applicants invention. l

Referring now to the drawings and in particular Figure 1, a portion of the internal combustion engine is indicated at 10. The valve gear portion of the engine comprises a rocker erm 11 which oscillates upon rocker arm shaft 12 which is connected in a well-known manner to the internal combustion engine 10. Oscillatory movement is imparted to the rocker arm through push rod 13 which has a semi-spherical end 14 to receive the end of adjusting bolt 16 threaded through one end of the rocker arm. Push rod 13 extends into a hollovved valve tappet 17 which is shown in greater detail in Figure 2. An annular shoulder 18 is provided axially spaced from the push rod end 19 upon which is mounted a coil spring 20 having a predetermined spring stiffness which urges the push rod apart from the valve tappet inner seat portion 21. Valve tappet 17 is, of course, provided with a curved bearing surface 22 which engages the base circle and/ or tapered lobe cam 22 on camshaft 23. To induce valve tappet rotation and eliminate edge contact and high loading between the cam lobe and the tappet bearing surface, the contact between the parts is on the centerline of the cam lobe offset from the centerline of the bearing surface. The other end of the rocker arm 11 has a cam-like surface 2S which engages the foot of a poppet valve 26 having the usual valve compression .spring 27 interposed between the internal combustion engine block 28 and a valve retainer 29 secured to the foot of the poppet valve 26 by locking members 31. The

- poppet valve 26 has the usual annular Valve portion 32 which engages the seat portion 33 in the cylinder block.

In actual operation, as the ltappet rides on the base circle of the camshaft, valve push rod tip 19 contacts the tappet seat portion 21. When the tappet leaves the base circle of the cam, the spring 20 urges the push rod yand tappet apart.

It can be seen, therefore, that lash problems, and in particular noise, are substantially minimized and controlled by applicants device. His construction is simple, effective, and adaptable for use in current used mechanical valve gear trains with a minimum of revision.

It will be understood that the invention is not to be limited to the exact construction shown and described, ybut that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

l. A mechanical valve gear for an internal combustion engine, said mechanical valve gear comprising a push rod, a spring and a valve tappet, said valve tappet having a cylindrical portion and an inner seat, said push rod being approximately axially aligned with said valve tappet and having an end portion with an annular shoulder formed thereon extending into the cylindrical portion of the valve tappet, said spring being interposed between the annular shoulder of the push rod and the inner seat of the valve tappet and biasing the push rod and valve tappet apart while permitting contact between the valve tappet and the inner end of the push rod under a predetermined valve gear load.

2. In an internal combustion engine, a mechanical motion transmitting device comprising a push rod, a valve tappet and a spring, said push rod having one end adapted to engage an oscillating member and another end which includes a spring engaging means, said spring engaging means being disposed intermediate of the push rod ends, said valve tappet member having an inner seat and an outer bearing surface adapted to engage a rotary cam, said spring being disposed between the push rod spring engaging means and the valve tappet inner seat and resiliently biasing said push rod and said valve tappet in 3, Y opposite directions, said spring having a predetermined stiffness which' permits the" push rod` t'oc'onta'c't the'A vl've tappet when the mechanicalE motion transmitting device loadexceeds a predeterminedvalue. i Si. Ih an' 'internaleomlustionengine; ajvalve'gear comprising Ia push rod, av valve tappe't"having` an'iiiner' s'eat and' anoute'rbea'ririg'surface adaptedto engageY a rotary cam; a" coiledv spring, s'aidl push" r'od having one end adaptedto engage anoscirllatingmemer and a'noth'ei' end engagng'the inner'sea't of the valve tappet'whentheva'lve gear load exceeds a predetermined va1ue',` spring' anchoringmeans exteriorly disposed on said'pushjrod between theends of the push rod andI adjacent t'otizie'end of the References Citedin the le of this patent UNITED STATES PATENTSrv Bishop Sept; 1'1f', H51 Russell- Apr. 26, 1955 

